Semiconductor memories are used in integrated circuits for electronic applications, including radios, televisions, cell phones, and personal computing devices, as examples. One type of semiconductor memory device is magnetoresistive random access memory (MRAM), which involves spin electronics that combines semiconductor technology and magnetic materials and devices. The spins of electrons, through their magnetic moments, rather than the charge of the electrons, are used to indicate bit values.
A typical MRAM cell may include a magnetic tunnel junction (MTJ) stack, which includes a pinning layer, a pinned layer over the pinning layer, a tunnel layer over the pinned layer, and a free layer over the tunnel layer. During the formation of the MRAM cell, a plurality of blanket layers is first formed. The blanket layers are then patterned by a photo etching to form the MTJ stack. A cap dielectric layer is then formed on the sidewalls, and possibly over the top surface, of the MTJ stacks, and the MTJ stack is protected by the cap dielectric layer.